Evaluating habitat preferences of three declining grassland sparrow species

Abstract

Grassland, prairie, and savannah ecosystems have been destroyed and degraded across North America as a direct result of colonization and subsequent urbanization and agricultural expansion. Consequently, the wildlife that once inhabited these ecosystems commonly are now among the most threatened in the planet. Grasshopper sparrow, Dickcissel and Henslow’s sparrow are three species of sparrow that have undergone dramatic population decreases within the last century and are considered species of greatest conservation need in Michigan. There is disagreement among land managers as to the best management practice for these species across the remnant and restored grasslands of Michigan’s lower peninsula because management for each species respectively can be detrimental to the others. In this study I conducted bird point counts to gather data on where these three species were occurring across 13 potentially suitable grassland sites in southern Michigan. Data on several vegetation characteristics was also gathered at each point. I found that Grasshopper sparrows occur more frequently in areas with more open habitat characteristics in terms of vegetation height and volume. Dickcissels occurred in areas with comparatively high levels of bare ground. Results were inconclusive on associations between Henslow’s sparrow presence and vegetation characteristics. I propose mid-summer haying on a 1-3 year cycle, haying up to 80 acre parcels of the managed area at a time along with occasional burning as a sufficient management technique for maximizing the habitat for (and promoting the coexistence of) all three of these bird species.